Cargo

Cargo networks are second only to electrical networks in terms of usefulness. They allow the transport of items to and from things like machines and barrels. They share many mechanics with their electrical siblings. At the heart of it is a Cargo Manager. As with electrical networks, it has a fixed range that can be extended with an item, in this case connector nodes.
Here is a sample system that shows the necessary components:

Yellow: Cargo manager

Red: Output node. This places items into whatever inventory it is attached to

Green: Connector node. These extend the network in the cardinal directions

Blue: Input node. Removes items from the inventory it is attached to

Protips

The range of a connector is 6 blocks. This means you can leave 5 blocks between them and remain connected.

Item transport is nearly instantaneous, occurring every 4 ticks and is equally fast whether there's just one item or a stack.